Two-way synthesis of a double-lantern heterobimetallic complex [Pd(μ-OOCMe)4Co]2(μ-OOCMe)2Pd(py)2

Article abstract of DOI:10.1016/j.inoche.2007.05.004

The lantern complex Pd^II(μ-OOCMe)₄Co^II(NCMe) (1) was transformed into the pentanuclear double-lantern acetate-bridged heterobimetallic complex [Pd(μ-OOCMe)₄Co]₂(μ-OOCMe)₂Pd(py)₂ (py is pyridine) (2) by two routes: (i) reaction of 1 with pyridine and (ii) reaction of 1 with trans-Pd(py)₂(OOCMe)₂. Complex 2 × 3C₆H₆ was characterised by single-crystal X-ray diffraction, DTA-TG and magnetic susceptibility data.

Full text of DOI:10.1016/j.inoche.2007.05.004

Inorganic Chemistry Communications 10 (2007) 948–951
www.elsevier.com/locate/inoche
Two-way synthesis of a double-lantern heterobimetallic complex
Pd(l-OOCMe) Co] (l-OOCMe) Pd(py)
[
4
2
2
2
a
a
a
Sergei E. Nefedov , Ilya A. Yakushev , Natalia Yu. Kozitsyna ,
Zhanna V. Dobrokhotova , Vladimir N. Ikorsky , Michael N. Vargaftik a,*,
a
b,
z
a
Ilya I. Moiseev
a
N.S. Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, Leninsky prospect 31, 119991 Moscow, Russian Federation
b
International Tomographic Center, Siberian Branch, Russian Academy of Sciences, 630090 Novosibirsk, Russian Federation
Received 28 March 2007; accepted 6 May 2007
Available online 18 May 2007
Abstract
The lantern complex Pd (l-OOCMe) Co (NCMe) (1) was transformed into the pentanuclear double-lantern acetate-bridged hetero-
II
II
4
bimetallic complex [Pd(l-OOCMe)
4
Co]
2
(l-OOCMe) (py is pyridine) (2) by two routes: (i) reaction of 1 with pyridine and (ii)
2
Pd(py)
2
reaction of 1 with trans-Pd(py)
netic susceptibility data.
2
(OOCMe)
2
. Complex 2 · 3C H was characterised by single-crystal X-ray diffraction, DTA-TG and mag-
6 6
ꢀ
2007 Elsevier B.V. All rights reserved.
Keywords: Heterobimetallic acetate complexes; Palladium; Cobalt; Pyridine; X-ray structure; Magnetic susceptibility; Thermogravimetry
Palladium(II)-based heterometallic complexes containing
transition metals attract attention as potential precursors for
the preparation of mixed-metal catalysts and nanomaterials
The labile axial ligands L = MeCN or H O bound to the
2
pentacoordinated metal atom were expected to be easily
replaced by stronger monodentate O,N-bases without any
noticeable change in the complex structure. We have previ-
ously found that bidentate 1,10-phenanthroline (phen)
[
1,2]. Recently we have synthesised and structurally charac-
II
terised a series of heterobimetallic Pd -based lantern-type
II II
II
II
complexes of the general formula Pd M (l-OOCMe) L
reacts with the complex Pd Co (l-OOCMe) (NCMe) (1)
4
4
(
M = Mn, Co, Ni, Zn; L = H O, MeCN) [3]. In these com-
in such a way that phen attaches to the cobalt(II) rather
than to the palladium(II) atom [5], substituting the axial
MeCN ligand and breaking one of four acetate bridges
and producing a triply bridged complex (MeCOO)Pd-
2
II
II
plexes the Pd and M atoms are drawn together by four
˚
acetate bridges, so that the PdÁ Á ÁM distances (2.46–2.68 A)
are close to the sum of covalent radii, implying some
metal–metal interaction. Such a structure is favourable for
keeping together the constituent metal atoms during chemi-
cal and thermal transformations. For example, the complex
(l-OOCMe) Co(phen) in which a rather short PdÁ Á ÁCo dis-
3
˚
tance in the Pd(l-OOCMe) Co moiety (2.69 A) was only
3
slightly elongated compared to 1. Continuing our studies
II
II
II
Pd Zn (l-OOCMe) (OH ) was easily reduced with H to
of the reactivity of the Pd -based heterobimetallic com-
4
2
2
afford a catalytically active PdZn nanoalloy under fairly mild
plexes, we checked the strength of the quadruply bridged
II
II
conditions (10% H /He, 150 ꢁC) [4].
Pd (l-OOCMe) Co system in reactions with other
2
4
N-bases.
Here we report the reaction of 1 with a monodentate
N-base, pyridine (py). Based on the precedent reaction of
*
Corresponding author. Tel.: +7 495 9554865; fax: +7 495 9541279.
E-mail address: wahr36@mail.ru (M.N. Vargaftik).
Deceased.
1
with 1,10-phenanthroline, the pyridine molecule was
z
expected to readily substitute the axial ligand L = MeCN
1
387-7003/$ - see front matter ꢀ 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.inoche.2007.05.004

S.E. Nefedov et al. / Inorganic Chemistry Communications 10 (2007) 948–951
II II
949
˚
˚
in 1, while the quadruply bridged Pd (l-OOCMe) Co
THF (Pd–O: 1.999(3) A; Pd–N: 2.029(4) A) [10]. The single
pentanuclear carboxylate-bridged mixed-metal complex
with similar structure [Cu(l-OOCH Cl) Y] Cu(ClCH -
4
moiety will not be corrupted. However, we unexpectedly
found that this reaction [6], unlike that with phen, pro-
duced a new complex [Pd(l-OOCMe) Co] (l-OOCMe) -
2
4
2
2
COO) (H O) that is known to us was isolated from the
4
2
2
8
2
8
Pd(py) (2).
reaction of mononuclear copper and yttrium nitrates with
sodium chloroacetate in aqueous solution [11].
This work demonstrates an example of the design of
multinuclear mixed-metal complexes using a mononuclear
carboxylate metal complex as the linking agent for hetero-
bimetallic lantern complexes bearing a labile donor ligand
or a vacant orbital.
2
The reaction suggests that a portion of 1 undergoes a
nucleophilic attack by py on the Pd atom to break the qua-
druply bridged Pd(OOCMe) Co system, producing a vir-
tual mononuclear diacetato-bis(pyridine)palladium(II)
species. The latter reacts with the rest molecules 1, substi-
tuting the labile axial MeCN ligand by the donor O atom
of the coordinated MeCOO group and linking two mole-
cules of 1 into pentanuclear complex 2. To verify this sug-
gestion, we performed a direct reaction between 1 and
separately prepared trans-Pd(py) (OOCMe) . The reaction
4
Molecules 2 are connected in the crystal 2 · 3C H
6
6
through weak contacts of the lantern Pd atoms with one
of three solvate C H molecules, forming infinite 1D chains
6
6
˚
(PdÁ Á ÁC ꢀ 3.1 A) (Fig. 2), while two other C H molecules
2
2
6
6
[
7] also afforded 2 in good yield. In both the cases 2 was iso-
lated from the reaction solution as the crystal solvate
· 3C H .
of crystallization are located in the crystal voids and have
no close contacts with molecules 2.
2
Complex 2 is paramagnetic [12]. The effective magnetic
moment decreases monotonically from 7.21 to 5.18 MB
in the temperature interval 300–2 K corresponding to two
6
6
Hence, complex 2 was prepared by two methods: (i)
reaction of 1 with py and (ii) reaction of 1 with the complex
trans-Pd(py) (OOCMe) :
II
magnetically independent Co centers with spin 3/2 and
2
2
Me
Me
C
Me
C
O
Me
C
Me
C
C
O
O
O
O
Me
C
O
Me
C
N
O
O
O
O
O
O
N
O
Co
py
Pd
Co
NCMe
O
O
Co
O
Pd
Pd
O
O
O
O
i
Pd
O
O
C
O
O
C
C
C
O
O
O
O
Me
Me
C
C
Me
C
Me
Me
1
Me
Me
2
Me
C
O
Me
C
O
O
O
O
N
ii
O
Pd
Co
NCMe
+
MeCOO
Pd OOCMe
O
O
N
C
C
Me
Me
1
i: benzene, room temperature (yield 40%)
ii: benzene, room temperature (yield 65%)
X-ray crystallography [8] (Fig. 1) showed that molecule
a substantial contribution of spin–orbital interactions and
intermolecular antiferromagnetic exchange at low tempera-
tures (Fig. 3).
2
(
2
consists of two heterodinuclear lantern moieties PdCo
˚
l-OOCMe) (Pd–O: 2.000(3)–2.010(3) A; Co–O: 2.060(3)–
4
˚
.085(3) A) connected to each other through two bridging
Crystals 2 · 3C H easily lose the solvation C H mole-
6
6
6
6
˚
acetate ligands (Co(1)–I(9): 2.003(3) A) belonging to the
cules upon storage in air at room temperature for 6–10 h.
The DTA-TG study [13] showed that complex 2 (free of
the solvation C H ) is stable upon heating to 90 ꢁC under
˚
central trans-Pd(py) (OOCMe) linker (Pd–O: 2.011(2) A;
2
2
˚
Pd–N: 2.022(3) A). The Pd–Co distance in molecule 2
6
6
˚
(
PdÁ Á ÁCo: 2.5418(7) A) is practically the same as that in
Ar. Further heating under Ar produced (i) elimination of
one py ligand at 90–160 ꢁC (weight loss 6.9% with a weak
endotherm); (ii) rearrangement of 2 after the loss of one py
ligand and the elimination of about half of MeCOO ligands
at 160–190 ꢁC (weight loss 25.2% with a strong two-stage
endotherm); (iii) elimination of the second py ligand at
190–250 ꢁC (weight loss 6.0% without noticeable thermal
˚
˚
molecule 1 (PdÁ Á ÁCo 2.515(3) A, 2.551(3) A in two indepen-
dent molecules in crystal 1).
The bond distances in the central fragment Pd(OOC-
Me) (py) are close to those in 1, trans-Pd(py) (OOC-
2
2
2
˚
˚
Me) · H O (Pd–O: 2.009(3) A; Pd–N: 2.021(3) A) [9] and
2
2
the adduct Pd(OOCMe) (py) · {Pd(py) [B(C F )2]} ·
2
2
4
6 5

950
S.E. Nefedov et al. / Inorganic Chemistry Communications 10 (2007) 948–951
Fig. 1. Molecular structure of complex 2 with hydrogen atoms omitted for clarity. The thermal ellipsoids are shown at 50% probability (symmetry
transformations used to generate equivalent atoms: #1 Àx, Ày, Àz; #2 Àx + 1, y À 1, Àz + 1).
6 6
Fig. 2. Fragment of a chain formed by molecules 2 linked through a solvate benzene molecule in the crystal 2 · 3C H .
sponds to transformation of 2 to Pd metal and CoO (calcu-
lated weight loss 60.4%). XRD [14] confirmed that the final
products of decomposition of 2 at 500 ꢁC are Pd metal and
CoO. The reflections from Pd metal and CoO crystallytes
are rather broad. Based on the most intense lines (111)
and (200), the average sizes of the Pd and CoO crystallites
were estimated by the Scherrer equation b = Kk/Lcosh as
at most 5–10 nm. Hence, the solid material produced by
thermal decomposition of 2 seems to consist of the Pd
metal and CoO nanoparticles.
7
6
6
5
5
.0
.5
.0
.5
.0
Acknowledgements
The authors thank the financial support from the Rus-
sian Foundation for Basic Research (Projects nos. 05-03-
0
50
100
150
200
250
300
T (K)
32983, 06-03-32578, 06-03-32742 and 06-03-08173), the
Fig. 3. Magnetic susceptibility of complex 2 in the range 2–300 K.
Foundation of President of the Russian Federation (pro-
gram for Support of Leading Russian Scientific Schools,
grant NSh-4959.2006.03) and the Russian Academy of Sci-
ences (programs for Basic Research ‘‘Purposeful Synthesis
of Inorganic Substances and Creation of Related Func-
effect); (iv) final decomposition in the interval 250–380 ꢁC
weight loss 29.0% with complex thermal effects). The total
weight loss upon heating to 500 ꢁC (61.1 ± 1.5%) corre-
(

S.E. Nefedov et al. / Inorganic Chemistry Communications 10 (2007) 948–951
951
tional Materials’’ and ‘‘Theoretical and experimental inves-
tigation of the nature of chemical bonding and mechanisms
of important reactions and processes’’).
of Pd
and the reaction mixture was magnetically stirred at room temper-
ature for 15 min until a light-yellow precipitate of trans-Pd(py)
3 6
(OOCMe) (50 mg, 0.2 mmol based on Pd) in benzene (10 ml)
2
-
(
OOCMe)
2
· H
2 4
O formed. A solution of PdCo(OOCMe) (NCMe)
(
212 mg, 0.48 mmol, 20% excess) in benzene (15 ml) was added to this
Appendix A. Supplementary material
suspension and magnetically stirred for 0.5 h to produce a purple
solution. The solution was filtered and kept for crystallization at
room temperature for 24 h. The crystals of 2 · 3C
from the mother liquor and used for X-ray diffraction study. An
additional portion of 2 · 3C was obtained by precipitation with
6 6
H were separated
CCDC 641937 contains the supplementary crystallo-
graphic data for 2 · 3C H . These data can be obtained
6
6
6
H
6
free of charge via http://www.ccdc.cam.ac.uk/conts/
retrieving.html, or from the Cambridge Crystallographic
Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK;
fax: (+44) 1223-336-033; or e-mail: deposit@ccdc.cam.
ac.uk. Supplementary data associated with this article can
be found, in the online version, at doi:10.1016/j.inoche.
hexane. Total yield 206 mg (65% based on Pd). Anal. for 2 (free of
C H ): Found (%): C, 30.56; H, 3.48; N, 2.23. Pd Co C30O20H40N .
6
6
3
2
2
À1
Calc. (%): C, 30.39; H, 3.40; N, 2.36. IR (KBr), m/cm : 2984w, 1621s,
1
7
576w, 1552m, 1450w, 1405vs, 1340m, 1211w, 1150w, 1071w 1026w,
64m, 716w, 695s, 624m.
[
6 6
8] X-ray structure analysis of 2 · 3C H : Bruker AXS SMART 1000,
˚
CCD-detector k(Mo Ka) = 0.71073 A, graphite monochromator, x-
2
007.05.004.
scanning, 2h
= 54ꢁ. C48H58Co N O Pd , M = 663.82, triclinic,
max
ꢀ
2
2
20
3
˚
˚
˚
space group P1, a = 8.2681(18) A, b = 10.465(2) A, c = 16.421(4) A,
a = 98.692(8)ꢁ, b = 97.223(7)ꢁ, c = 91.174(8)ꢁ, V = 1392.2(5) A
˚
3
References
3
(
110E), Z = 1, Dcalc = 1.694 g/cm , 12364 measured reflections, 4684
2
À1
independent reflections with F > 2r(I), l = 1.607 cm , R
wR
16]. The structure was solved by the direct method and refined by the
1
= 0.0439,
[
[
[
[
1] J.M. Thomas, W.J. Thomas, Principles and Practice of Heteroge-
neous Catalysis, VCH, New York, 1997.
2] J.H. Sinfelt, Bimetallic Catalysts. Discoveries, Concepts and Appli-
cations, Wiley, New York, 1983.
3] N.Yu. Kozitsyna, S.E. Nefedov, F.M. Dolgushin, N.V. Cherkashina,
M.N. Vargaftik, I.I. Moiseev, Inorg. Chim. Acta 359 (2006) 2072–2086.
4] O.P. Tkachenko, A.Yu. Stakheev, L.M. Kustov, I.V. Mashkovsky,
M. van den Berg, W. Gr u¨ nert, N.Yu. Kozitsyna, Zh.V. Dobrokhot-
ova, V.I. Zhilov, S.E. Nefedov, M.N. Vargaftik, I.I. Moiseev, Catal.
Lett. 112 (2006) 155–161.
2
= 0.1071. Corrections for absorption were made by SADABS
[
2
full-matrix least squares method for F with anisotropic parameters
for all non-hydrogen atoms. All calculations were performed with the
use of the SAINT [17] and SHELXTL-97 [18] program packages.
9] S.V. Kravtsova, I.P. Romm, A.I. Stash, V.K. Belsky, Acta Crystal-
logr. C 52 (1996) 2201–2204.
[
[
[
[
10] Liging Ma, R.C. Smith, J.D. Protasiewicz, Inorg. Chim. Acta 358
2005) 3478–3482.
11] Cun-Gen Zhang, Deyue Yan, Yilin, Fengyue. Yang, J. Coord. Chem.
1 (2000) 261–269.
(
[
[
5] S.E. Nefedov, M.N. Vargaftik, I.I. Moiseev, Inorg. Chem. Commun.
5
9
(2006) 755–757.
6] Synthesis of 2 by method 1. To a suspension of PdCo(OOC-
Me) (NCMe) (210 mg, 0.5 mmol) (prepared according to [3]) in
12] Magnetic susceptibility was measured on a SQUID magnetometer
MPMS-XL ‘‘Quantum Design’’ in the temperature interval 2–300 K
at a magnetic field strength of 5000 Oe.
4
benzene (15 ml) was added pyridine (40 mg, 0.5 mmol) under stirring.
The reaction mixture was magnetically stirred for 15 min at room
temperature to produce a purple solution, which was filtered and kept
for crystallization for 12 h at room temperature. The purple-red
[
13] DTA-TG measurements were performed on DSC-20 and TG-50 units
of a thermoanalyzer TA-3000 (Mettler) under argon with a rate of
À1
5ꢁ min
.
[
14] XRD was studied on a focusing Guinier camera FR-552 (Cu Ka1
radiation, germanium as an the internal standard). The diffraction
pattern was measured on a comparator IZA-2 (LOMO, St.-Peters-
burg, Russia) with an accuracy of 0.01 mm and indexed using the
program TREOR 90 [15].
crystals of 2 · 3C
for X-ray diffraction study. An additional portion of fine-crystalline
· 3C was obtained after storage of the mother liquor at +15 ꢁC
for 24 h. Total yield: 94 mg (40% based on Pd). Anal. for 2 · 3C
Found (%): C, 40.52; H, 4.18; N, 2.03. Pd Co . Calc. (%):
C, 40.60; H, 4.12; N, 1.97. The crystals of 2 · 3C readily lose the
crystallization benzene molecules after storage in air at room
temperature for 6–10 h. Anal. for 2 (free of C ): Found (%): C,
. Calc. (%): C, 30.39; H,
6 6
H were separated from the mother liquor and used
2
6 6
H
H :
6 6
3
2 48 20 58 2
C O H N
[
[
[
15] P.-E. Werner, L. Eriksson, M. Westdahl, J. Appl. Crystallogr. 18
6 6
H
(
1985) 367–370.
16] G.M. Sheldrick, SADABS, 1997, Bruker AXS Inc., Madison, WI-
3719, USA.
6
H
6
5
3
3
1
3 2 30 20 40 2
0.67; H, 3.58; N, 2.13. Pd Co C O H N
.40; N, 2.36. IR (KBr), m/cm : 2986w, 1622s, 1576w, 1552m, 1451w,
405vs, 1341m, 1211w, 1150w, 1072w 1026w, 764m, 716w, 696s, 624m.
17] SMART V5.051 and SAINT V5.00, Area detector control and
integration software, 1998, Bruker AXS Inc., Madison, WI-53719,
USA.
À1
[
2 2
7] Synthesis of 2 by method 2. The complex trans-Pd(py) (OOCMe)
was prepared according to [9] and used without separation from the
reaction mixture. Pyridine (32 mg, 0.4 mmol) was added to a solution
[
18] G.M. Sheldrick, SHELXTL-97 V5.10, 1997, Bruker AXS Inc.,
Madison, WI-53719, USA.